1. Field of the Invention
The present invention relates generally to vehicle suspension systems. More particularly, the present invention relates to a front suspension fork assembly especially well-suited for use in connection with a straddle-type vehicle.
2. Description of the Related Art
Many types of vehicles utilize one or more suspension assemblies operably positioned between one or more wheels of the vehicle and the body of the vehicle. The suspension assemblies improve operator control by absorbing bumps, or other irregularities, in the surface that the vehicle is traversing. Straddle-type vehicles, such as motorcycles or motor scooters, for example, and other types of vehicles employing a single front wheel often use a telescopic front fork suspension assembly to absorb bumps encountered by the front wheel.
Such suspension fork assemblies typically include a pair of fork legs arranged on opposing sides of the front wheel. Each fork leg includes an upper fork tube telescopically engaged with a lower fork tube. A separately formed bracket member interconnects an upper end of the fork legs and is coupled to a steering assembly of the vehicle. The front wheel of the vehicle is usually supported by a lower end of the fork legs. Impact forces are imparted on the front wheel as the vehicle encounters bumps, or other irregularities, of the surface on which it is traversing. These forces are transferred to the junction of the bracket member and the upper fork tubes. Therefore, high strength in this area of the fork assembly is important.
In a typical prior art suspension fork assembly, the upper fork tubes and interconnecting bracket are an assembly of individual members. For instance, the upper fork tubes are often clamped or press fit into receiving apertures of the interconnecting bracket. Such a construction necessitates an additional manufacturing step to assemble the upper fork tubes to the interconnecting bracket and, thus, increases over all manufacturing costs of the vehicle. Furthermore, the upper ends of the upper fork tubes are usually supported at a height below an upper surface of the central portion of the interconnecting bracket. Thus, the bracket usually extends in a downward direction from the central portion to each fork leg. As a result, the potential cross-sectional contact area between the interconnecting bracket and each upper fork tube is necessarily limited. Thus, the overall strength of the fork assembly is also limited.
Advantageously, preferred embodiments of the present suspension fork assembly include upper fork tubes and an inner connecting portion, or support bridge, which are of a one-piece construction. Such an integrated arrangement permits cost-effective manufacture of the suspension assembly. In addition, desirably, an upper end of each upper fork tube extends above an upper surface of the central portion of the interconnecting portion, or support bridge. Accordingly, the support bridge may extend substantially horizontally from its central portion to each upper fork tube, thereby increasing the cross-sectional contact area between the support bridge and the upper fork tubes. Advantageously, with such an arrangement, the strength of the fork assembly is increased.
In a modification of the above-described preferred suspension fork assembly, a biasing member is positioned within the upper fork tube and is arranged to bias the upper fork tube and lower fork tube apart from one another. Preferably, at least a portion of the biasing member occupies a space defined by the upper end portion of the upper fork tube, which extends above the upper surface of the support bridge. Accordingly, such a suspension fork arrangement may possess a lower overall height while providing the same amount of suspension travel as a conventional suspension fork assembly, wherein the upper tubes do not extend above the interconnecting bracket.
An aspect of the present invention involves a front suspension fork assembly for a vehicle. The suspension fork is configured for attachment to a steering tube of the vehicle at an upper end and for supporting a front wheel of the vehicle at a lower end. The suspension fork comprises a pair of fork legs, each fork leg including an upper fork tube and a lower fork tube. The upper fork tubes are telescopingly engaged with the lower fork tubes. A support bridge interconnects the upper fork tubes and the support bridge and the upper fork tubes are monolithically formed. A central portion of the support bridge surrounds the steering tube and an upper end portion of each upper fork tube extends to a height above a height of the central portion of the support bridge.
Another aspect of the present invention involves a front suspension fork assembly for a vehicle. The suspension fork is configured for attachment to a steering tube of the vehicle at an upper end and for supporting a front wheel of the vehicle at a lower end. The suspension fork comprises a pair of fork legs, each fork leg including an upper fork tube and a lower fork tube. The upper fork tubes are telescopingly engaged with the lower fork tubes and a support bridge interconnects the upper fork tubes. The support bridge and the upper fork tubes are monolithically formed. The support bridge comprises a central portion surrounding the steering tube and an intermediate portion extending between the central portion and each upper fork tube. An upper surface of the intermediate portion is substantially normal to an axis of the fork tube.
A further aspect of the present invention involves a scooter having a front wheel, at least one rear wheel, and a frame. The frame comprises a head tube configured to rotatably support a steering tube. A front suspension fork assembly is attached to the steering tube at an upper end and supports a front wheel of the vehicle at a lower end. The suspension fork comprises a pair of fork legs, each fork leg including an upper fork tube and a lower fork tube, the upper fork tubes being telescopingly engaged with the lower fork tubes. A support bridge interconnects the upper fork tubes, the support bridge and the upper fork tubes being monolithically formed. A central portion of the support bridge surrounds the steering tube and an upper end portion of each upper fork tube extends to a height above a height of the central portion of the support bridge.
Yet another aspect of the present invention involves a scooter having a front wheel, at least one rear wheel, and a frame. The frame comprises a head tube configured to rotatably support a steering tube. A front suspension fork assembly is attached to the steering tube at an upper end and supports a front wheel of the vehicle at a lower end. The suspension fork includes a pair of fork legs, each fork leg including an upper fork tube and a lower fork tube. The upper fork tubes are telescopingly engaged with the lower fork tubes. A support bridge interconnects the upper fork tubes. The support bridge and the upper fork tubes are monolithically formed. The support bridge comprises a central portion surrounding the steering tube and an intermediate portion extending between the central portion and each upper fork tube. An upper surface of the intermediate portion is substantially normal to an axis of the fork tube.